Electronic circuit



1, 9- s. c. HURLEY, JR 2,460,456

ELECTRONIC CIRCUIT Filed Jan. 4, 1947 AAAAAA MAMA "vvv

INVENTOR. SAM EL QHURLEX Je. BYWZ & Mill/0 A TTURNEY? Patented Feb. 1, l949 ELECTRONIC ,cIRcU-r'r Samuel C. Hurley, Jr., Danville, 111.; Wilmina L. Hurley, executrix of said Samuel C. Hurley, Jri, deceased; assignor to Wilmina L. Hurley, Dan- Application January 4, 1947', Serial. No. 120,230

g 1 Claim. (01. 315207) This invention relates to a means for deionizing a gas-filled tube once it is ionized, It particularly relates to an electronic circuit in which a vacuum tube is connected in parallel with a gas-filled tube across a source of direct current potential.

One of the problems in this art is the deionization of a gas-filled tube which is connected across a source of direct current potential, once it is ionized. In many operations such'as photoelectric inspection operations, registration control operations. and others, it is necessary to deicnize the tube at certain intervals or under certain conditions. It is a characteristic of a gas-filled tube which is connected. to a source of direct current potential that once it is ionized, it will continue to ionize until the circuit is broken regardless of how negative in potential the control grid is driven. In the prior art, mechanical switches, time delay relays and other mechanical devices have been used to interrupt the circuit and thereby deionize the gas-filled tube. However such mechanical switches or anything involving mechanical means for interrupting the circuit, have the usual disadvantages that Mechanical are inherent in mechanical means. means are never as instantaneous in their reaction as electronic means. Mechanical means require more upkeep and if a switch sticks, the desired result is not obtained. There is nothing to go wrong with electronic means such as is 1? described herein. Electronic means are instan-- taneous and will always respond in the required manner,

Broadly my invention comprisesia vacuum tube connected in parallel with a gas filled tube across l l a direct current source of potential. The gas filled tube is controlled by a grid and once it is ionized, it will, continue to ionize unless something is done to deionize it, A vacuum tube isconnected in parallel with the gas-filled tube and if a sufficient positive bias is placed on the control grid of the vacuum tube, the vacuum tube will. draw all the current through the parallel circuit and leave no current to flow through the gas-filled tube and therefore the The choke coil has the characteristic of always drawing the same amount of current and by such an arrangement when the vacuum tube draws current below that which would normally be drawn by the choke coil there is no current left to flow through the gas-filled tube and, it will deionize.

It. is therefore an object of this invention to provide an improved means for deionizing a gas filled tube once it is ionized.

Other advantages, objects and uses of my. invention will become apparent by referring to the. drawing. For sake of illustration the drawing is described in connection with photoelectric means for controlling the grid in the vacuum tube and in the gas-filled tube. However, it is distinctly understood that any means depending. uponlthe kind of operation and the results desiredmay be employed to control the control grids of the amplifying tubes. The invention resides in the particular means for deionizing the g,asfilled tube once the gas-filled tube. is ionized.

Agas-filled' tube It] is provided having an anode circuit ll, a cathode circuit I2. and a control grid i3. It is connected to. a source of direct current having its positive terminal atv It and grounded at. 1.5... The control grid l3 in this particular illustration is controlled by a photoelectric circuit employing a phototube l5 con-- nested in series with the resistor I I 6 across a.

source of direct current potential having its positive terminal at I and its negative terminal at I8 The grid. [.3 is connected between the phototube I5 and the resistor It at the point. l9. When the tube i5 is in shadow, a negative potential is placed on the control grid l3 which will prevent'the tube It from ionizing or conducting a current. When the tube 55 is in light, a. positive potential is placed on the control grid l3 and if the circuit otherwise is properly adjusted or controlled, current will flow through the tube it.

A vacuum tube. 21! is also provided having an anode. circuit 2!, a cathode circuit 22 and a control grid 23. The vacuum tube 20 is'connected in parallel with the gas filled tube I l! and the two circuits are joined at the ground I5 and at the point 24. The control grid 23 may be changed from negative to positive depending upon the type of operation by any desired means but for illustrative purposes the following circuit is employed to demonstrate how the device works. A second vacuum tube 25 is provided having an anode circuit 26, a cathode circuit 21 and a control grid 28. The tube 25 is connected to a source of direct current potential having its positive terminal at 29 and grounded at 3B, The vacuum tube 2-5 is connected in series with the load resister SH and the biasing resistor 32. The control grid 23 is connected at the point 33 between the load resistor 3i and the anode 26. The tubes 20 and 25 are so connected that they are 180 out of phase. That is, when tube 25 conducts a current, tube 20 is non-conducting and when the tube 25 is non-conducting, tube 2c is rendered conducting. The control grid 28 is connected to point 34 between. the phototube 35 and the resistor 36. The series circuit employing the phototube 35 and resistor 36 is connected to a source of direct current potential having its positive terminal at 3? and its negative terminal at 38.

The operation of the device is as follows: Normally the phototube 35 is in light which places a negative potential on the control grid 28 and a positive potential on the control grid 23. Thus the circuit involving tubes in and 211 are normally biased so that the voltage on the control grid I3 controls the flow of current through the tube Hi. When the phototube I5 is in darkness, no current will flow through the tube Hi. However when the phototube i5 is in light, current 9 potential is placed on the control grid 23. If a' high positive potential is placed on the control grid 23, the tube 20 will conduct all of the current through the parallel circuit leaving no current left to flow through tube Hi and it would become deionized. This is the condition when the phototube 35 is placed in darkness. When the tube 35 is again placed in light it will place a negative potential on control grid 23 and the circuit employing the tube In is again in condition to be controlled by the control grid l3.

In many operations particularly Where the circuit can be designed for a particular job, the tube 20 alone upon conducting a current will deionize tube 10. This occurs when the source of potential at 29 is sufliciently high to conduct a large quantity of current through tube as which will take all the current from the source Hi. However, particularly in circuits where conditions vary, and the exact design cannot be made for all circumstances, it is necessary to employ a choke coil in series with the parallel circuit involving tubes [9 and 20. Choke coil 39 is provided and is connected in series with the adjustable resistor 40 between the point l4 and the point 24. The amount of current which a choke 6 the control grid 23 will cause all the current to flow from the point M through the choke coil 39, the resistor 43, the tube 20 to the ground l5 leaving no current left to flow through the tube In and the tube ill will become deionized and ready for the next operation or inspection.

My invention resides in having a circuit in parallel with the gas-filled tube, such that said circuit can be caused to conduct all the current and leave no current left for the gas-filled tube to conduct. This is a rapid and accurate way for deionizing a gas-filled tube and a means is provided to insure. the deionization of the gasfilled tube at the time it is supposed to deionize for the particular operation being conducted.

Throughout the specification and claims whenever I speak of a positive or negative potential or a positive or negative bias, I mean the relative potential or bias of the control grid in respect with its cathode. The cathode and grid may both be at a positive potential but if the grid is more positive than the cathode, a positive bias or potential is placed on the grid. Likewise both may have a positive potential, but if the grid is less positive than the cathode, a relative negative potential is placed on the grid.

I claim as my invention:

An electronic circuit comprising a source of direct current, a vacuum amplifying tube, a gasfilled amplifying tube, said vacuum tube and said gas-filled tube being connected in parallel with said source of direct current, each of said tubes having an anode circuit, a cathode circuit, and a control grid, a choke coil and a resistor connected in series with said. parallel circuit including said vacuum tube and said gas-filled tube, a third amplifying tube having a loaded anode circuit, a cathode circuit and a control grid, the control grid of said vacuum tube being connected to the loaded anode circuit of said third amplify ing tube such that the two tubes are 18d out of phase, independent photoelectric voltage-applying means controlling the bias on the control grid of the gas-filled tube thereby controlling the ionization of the gas-filled tube. and means for preventing or stopping the flow of current through the gas-filled tube including voltageapplying means placing sufiicient negative bias on the control grid of the third amplifying tube such that the vacuum tube will conduct sufficient current from the direct current source or" potential to render the gas-filled tube non-conducting.

SAMUEL C. HURLEY, JR.

REFERENCES CITED UNITED STATES PATENTS 9 Number Name Date 2,30%,998 Gillespie, Jr Dec. 15, 194-2 2,356,195 Balsley Aug. 22, 1944 2,408,613 Dickinson Oct. 1, 1946 2,428,149 Falk Sept. 30, 1947 

